RECENT LASER PROPULSION RESULTS FROM … · “momentum calorimetry”, in which experiments like those accomplished here may be conducted to obtain reliable heats of formation. The

RECENT LASER PROPULSION RESULTS FROM

WSMR/HELSTF/PLVTS

August 2005

Bill LarsonAerospace Engineer

Propulsion DirectorateAir Force Research Laboratory

Edwards AFB, California

Distribution A – Approved for public release, Distribution Unlimited

Report Documentation Page Form ApprovedOMB No. 0704-0188

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1. REPORT DATE MAY 2005 2. REPORT TYPE

3. DATES COVERED -

4. TITLE AND SUBTITLE Recent Laser Propulsion Results from WSMR/HELSTF/PLVTS

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) C Larson

5d. PROJECT NUMBER 4847

5e. TASK NUMBER 0159

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Air Force Research Laboratory (AFMC),AFRL/PRSP,10 E. SaturnBlvd.,Edwards AFB,CA,93524-7680

8. PERFORMING ORGANIZATIONREPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)

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12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited

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Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18

2

File name

Abstract

On our 31st trip to the laser facility at WSMR we carried out experiments on laser ablation of black and white Delrin [also called polyoxymethylene, polyformaldehyde, (HCHO)x]. Mass ablation andthrust generation (Impulse) were accurately measured as a function of input laser energy in one shot experiments. The efficiency of conversion of laser energy to jet kinetic energy depended on thegeometry of the energy absorption/conversion zone. The most ideal geometry, an axis symmetric mini thruster, produced ~ 60 % conversion efficiency. The extensively studied 10-cm diameter Lightcraft (with inverted paraboloid, plug nozzle geometry) produced ~ 50% conversion efficiency. The upper limit to energy conversion was computed with CEA code to be 73% for the well defined mini thruster geometry. Thus, total losses amount to ~ 13% and ~ 23%. This is a significant finding and helps to validate the concept of “momentum calorimetry”, in which experiments like those accomplished here may be conducted to obtain reliable heats of formation. The performance of candidate chemically enhanced laser ablation or other solid propellants may be measured on a small scale. In these most recent experiments, a near-exact match of coupling coefficients (1%) was achieved in a 14-fold scale-down of the 10-cm Lightcraft to the mini thruster.


3

File name

Outline

• Collaboration Network/Why Laser Propulsion?• Flavor of PLVTS• The Laser and EL measurement (Joules)• The Pendulum and I measurement (Newton seconds)• The Mettler Balance and m measurement (milligrams)• Compare the EL, I, m measurements on 2 Test Articles

– Light Craft, model 200-3/4– Mini Thruster Standard for momentum calorimetry/prop devel

• Elementary considerations (energy/momentum)• Comparison of experiments to 1-D equilib code (CEA)• Conclusions/Work in progress/Flight Tests Movie


4

File name

Phase II Program CollaborationsPhase II Program CollaborationsXX--50LR: Experimental 5050LR: Experimental 50--cm Laser Ramjetcm Laser Ramjet

Vehicle FabricationCOI CeramicsDr. Tim Easler

System StudyFlight Unlimited

Mr. Dave Froning

Attitude ControlPolaris Sensors

Mr. John Harchanko

Ablation of Solid FuelsInst. of Technical Phys.

Mr. Wolfgang Schall

X – 50LRDr. Frank Mead, Jr.Dr. C. “Bill” Larson

AFRL/PRSP

Beam PropagationDS&S

Dr. Alan Pike

Ablation of Liquid FuelsInst. for Laser Technology

Dr. Shigeaki Uchida

Laser ConsultantTrex EnterprisesDr. Victor Hasson

Laser Propulsion for NavyMichael Libeau

NSWCDD, Dahlgren, VA

Laser LaunchersAFOSR MURIDr. Mitat Birkan

CO2 Laser: Lab & Flight TestingHELSTF/WSMR - Mr. Steve Squires

= Government Agencies= Contractors= Foreign Research

SiC ParabolasDARPA

Dr. Christodoulou

Computer Launch ModelPenn State U.

Dr. Michael Micci(Mr. Sean Knecht)

Thrust MeasurementU. Alabama, HuntsvilleDr. Andrew Pakamov


5

File name

Team December 2004Pulsed Laser Vulnerability Test System

Frank Mead, Bill Larson, AFRL/PRSPJim Shryne, RSIJohn Harchanko, POLARIS TECHNOLOGIESSteve Squires, Chris Beairsto, Mike Thurston, JaySpray, WSMR/HELSTF/PLVTS


6

File name

Overall Energy Conversion in Laser Propulsion Mission

Εf = 1/2mv2 = η α β γ δ Ewall

η= propulsion efficiency (jet kinetic energy to vehicle kinetic energy)α = expansion efficiency (internal propellant energy to jet kinetic energy)

β = absorption efficiency (laser energy at vehicle to internal propellant energy)γ = transmission efficiency (laser energy at ground to laser energy at vehicle)

δ= laser efficiency (electric energy to laser energy at ground)

***** Issue: separability of η α β γ δ and Ewall *****

“ $500 worth of electricity to put 1 kg into LEO.”At $0.10/KWH, $500 buys 18,000MJ = Ewall (1 KWH = 3.6 MJ);

1 kg at 10 km/s has Ef = 50 MJ, so ηαβγδ = 0.0028 = 50/18000But if 28% overall efficiency, then $5/kg

Phipps, Reilly, Campbell, Laser & Particle Beams 18 (2001) 661-695Pirri, Monsler, Nebolsine, AIAA Journal 12 (1974) 1254-1261


7

File name

Pulsed Laser Vulnerability Test System


8

File name

Laser Specifications

• Pulsed CO2 Laser• 10 KW• ~ 5 to 30 µs pulse width• Up to 30 Hz• Up to 1000 J/pulse (EL + 10%)• Near Field Burn Pattern

~ 10 feet


Pulse Shape

0

0.01

0.02

0.03

0.04

0.05

0 5 10 15 20time (µs)

Pow

er (a

rb u

nits

)

4 cm

25

9

File name

10 kW LASER IRRADIATION


10

File name

FFT and Far Field Burn Patterns

Burn Patterns:

10 c

m

1500 feet500 feet 1000 feetDistribution A – Approved for public release, Distribution Unlimited

11

File name

Pendulum Test Stand

10cm Aluminum Delrin y = 0.2043x R2 = 0.9997

0

0.05

0.1

0.15

0 0.2 0.4 0.6 0.8Maximum RVDT Volts

Impu

lse

(Ns)

0.14

0.19

0.24

0.29

0.34

RVD

T vo

ltage

Y=0.2043x R2 =0.9997

Impu

lse

(Ns)

RVDT Volts

RVD

T Vo

lts

0 3.30 3.3Time (s)


12

File name Comparison of Pendulum Impulse to Hammer Impulse

0 1 2 3 4 5 6 7 80.94

0.95

0.96

0.97

0.98

0.99

1.00

1.01

1.02

1.03

1.04

1.05

1.06

ratio

of p

endu

lum

mom

entu

m to

ham

mer

impu

lse

test artic le 1test artic le 2test artic le 3

Comparison of Pendulum Impulse to Hammer Impulse

Pendulum Deflection (degrees)

Rat

io o

f Pen

dulu

m M

omen

tum

to H

amm

er Im

puls

e Θ⎟⎟⎠

⎞⎜⎜⎝

⎛ π≅Θ−=

720Lgm)cosL(1gmI opend

opendpend

Larson, Mead AIAA 2001-0646Distribution A – Approved for public release, Distribution Unlimited

13

File name

NIST Traceable Impulse Calibration

0

0.1

0.2

1275 1300 1325 13500.07

0.1

0.13

0.16

0.19

time (ms)

Hammer

RVDT

Ham

mer

Vol

ts

RVD

T Vo

lts


14

File name

Mettler Balance or Digital Balance

Measure m to + 0.3 mg


15

File name

Model 200 Lightcraft Series:Model 200 Lightcraft Series:An AFAn AF--Patented Laser Vehicle ConceptPatented Laser Vehicle Concept


16

File name

Lightcraft and Mini-Nozzle StandardMini-nozzle

26o divergence angle200-3/4 Lightcraft

ε(ideal plug nozzle) = 14m=40g

Delrin surface area ~ 25 cm2

350 J/25 cm2/18 µs = 0.8 MW/cm2

Cm=450 N/MW, EL/m=5.1 MJ/kgVe= 2270 m/s, efficiency = 0.51T/W=CmP/mg = 11 at P=10 KW

ParabolicOptic

Focus

Shroud

Fore body

10g Delrin

5 cm

5 cm Delrin

0.64 g

ε = 8 ε = 16

ε= 8m=7.8 g

Delrin surface area ~ 0.71 cm2

25 J/0.71 cm2/18 µs = 2.0 MW/cm2

Cm=442 N/MW, EL/m=6.3 MJ/kgVe=2795, efficiency=0.62


17

File name

Laser Light Craft Flights


100 200 300 400 500coupling coef f icient (Ns/MJ)

0

10

20

30

40

50

altit

ude

(m)

tiime (s)

Laser Lightcraf t Flights w ith AirModel 200-3/4, M = 0.04 kg, 10 kW at 25 Hz, 400 J/pulse

1.0 s

0.0 s0.2 s

0.4 s

0.6 s

0.8 s

1.2 s1.

4 s

1.6

s1.

8 s2.

0 s2.

2 s

2.4

s

2.55 12.710.27.655.10T/W

Alti

tude

(m)

Coupling coefficient (Ns/MJ)

Light Craft Flights with Air or DelrinModel 200-3/4, m=40g 10kW at 25 Hz 400 J/Pulse50

30

20

0

10

40

10T/W=2.6 5.1 7.7 13

100 300200 400 500

Larson, Mead AIAA 2001-0646

18

File name

Air Plasma


19

File name

Mini Thruster 25 J, 18 µs, 0.71 cm2


20

File name

I, m, EL for Mini Thruster

Miniature Nozzle w ith black or w hite Delrin

I = 0.000444 ELR2 = 0.97

I = 0.000439 ELR2 = 0.98

I = 0.000253 ELR2 = 0.97

0.000

0.005

0.010

0.015

0 5 10 15 20 25 30laser energy (J)

Impu

lse

(Ns)

w hite

black

air

Miniature Nozzle w ith black or w hite Delrin

m = 0.000160 ELR2 = 0.99

m = 0.000156 ELR2 = 0.98

0

0.001

0.002

0.003

0.004

0.005

0 5 10 15 20 25 30laser energy (J)

mas

s ab

late

d (g

)

w hite

black

I/EL = 444 Ns/MJ m/EL = 0.160 mg/JVe = (I/EL)/(m/EL) = 2775 m/s

Efficiency = ½(I/EL)2/(m/EL) = 0.616 = αβΦ


21

File name

10 cm Light Craft 322 J, 18 µs


22

File name

I, m, EL for Light Craft 200-3/4

10 cm w hite and black Delrin

m = 0.000194 ELR2 = 0.93

m = 0.000201 ELR2 = 0.96

0.0000

0.0100

0.0200

0.0300

0.0400

0.0500

0.0600

0.0700

0 100 200 300 400EL (J)

Abla

ted

mas

s (g

)

black

w hite

10 cm w hite and black Delrin

I = 0.000447 ELR2 = 0.85

I = 0.000453 ELR2 = 0.92

0

0.05

0.1

0.15

0.2

0 100 200 300 400EL (J)

Impu

lse

(Ns)

black

w hite

I/EL = 447 Ns/MJ m/EL = 0.201 mg/JVe = (I/EL)/(m/EL) = 2224 m/s

Efficiency = ½(I/EL)2/(m/EL) = 0.497 = αβΦ


23

File name

CONVERSION OF LASER ENERGY TOJET KINETIC ENERGY

><><= 2

2Φ

e

evv

pmβEQ* L=

vC e 1αβΦ ½ ≤=><

∫

∫=

∫

∫=

∫

∫ ρ

ρ

ρ

ρ

ρ

f

i

f

if

i

f

i

f

im

m

m

mm

m

t

0

dm

)d(m

dm

dt -

dρ

)(d=><

ee

e

vFvv

∫

∫

fρ

iρ

fρ

iρ

dρ

)d(ρ=><

2

2e

e

vv

><αβΦ2=

><><

><αβ2

E=

2

2

L ee

e

e vvv

vIC ⎥⎦

⎤⎢⎣⎡=

Specific internal energy

Lp2

pjet αβEQ*αmm21E ==><= ev

Φαβ=><

><αβ= 2

2

LpE2m e

e2

vvI

><= evI pm

For propellants with chemical energy

( ) ⎟⎠⎞

⎜⎝⎛ +=

L

chem papparent E

∆umβαΦαβΦLarson, Mead, Kalliomaa,AIP Conference Proceedings, 664 (2003) pp170-181Distribution A – Approved for public release, Distribution Unlimited

24

File name Performance map of known laser materials and theoretical air

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000

exit v elocity v E = I/m (m/s)

0

100

200

300

400

500

600

700

800

900

1000

Cou

plin

g co

effi

cien

t C

m =

I/E

L N

s/M

J

AirBD27a.axg July 23, 2002 11:42:54 AM

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1 α β Φ

Phipps (proprietary)

1.00.90.80.7

0.60.5

0.40.3

0.2

α β Φ

equil ibrium

Phipps and Luke (2002) Black PVC

pryoxlyn

DLR Delrin PVC (PET) 44*

(PET)

2 M

J/kg

PVC (PET) 46*

Printer's ink

com pared to equilibrium ande fficie ncy for several solid prope llantsα β Φ

frozen blow dow n of air to 1 bar

0.16 M

J/kg

10 MJ/kg

40 MJ/kg

frozen

air blowdown

1 M

J/kg

3 M

J/kg

4 M

J/kg

5 M

J/kg

AFRL Delr

in

7 MJ/k

g

9 MJ/k

g

15 MJ/kg

20 MJ/kg

30 MJ/kg

Φ = 8/3π = 0.849Maxwell ian gas

8 MJ/k

g = (u c

- uo ) /

= E L

/m

β

50 MJ/kg

air blowdownfrozen equilibrium

60 MJ/kgResearchPropellants


Larson, Mead, Knecht, AIAA 2004-0649

αβΦ efficiency of several propellants comparedTo equilibrium and frozen blow down of air

½ CmVe=αβΦ, Cm=[m/EL]Ve

25

File name

Experimental Results December 2004200-3/4 Light Craft and Mini Thruster

6 7

EL/m (M

J/kg)

45

86 7

EL/m (M

J/kg)

45

8

EL/m (M

J/kg)

45

8

0100200300400500600700800900

1000

0 1000 2000 3000 4000

Ve(m/s)

Cm

(Ns/

MJ)

10 cm wht Delrin10 cm blk Delrinmini wht Delrinmini blk Delrinmini imp wtd whtmini imp wtd blk

1.0

0.6

0.4.

0.20.1

0.8

αβΦ

= 1/

2Cm

V e

0.9

0.7

0.5

0.3


26

File name Instantaneous Energy Addition to Delrin

4 mg per shot evaporated20 µm layer/18 µs6 J/mg = Q*/β

Specify energy and density of heated layerQ*delrin < 6 MJ/kg, ρ < 1420 kg/m3

Obtain P ~ 20,000 bar T ~ 3700 K via CEASpecify expansion ratio

ε = 4, 8, 16, 32, 64Obtain Isp, thermo props in exit plane via CEA


τp = 18 µsF = 35 J/cm2

I = 2.0 MW/cm2

EL=25 J

Del

rinρ

= 14

20 k

g/m

3

27

File name

6 J/mg Energy Addition to Delrin

Delrin (HCHO)n

Polyformaldehyde(cr, STP) [(HCHO)3]n

HCHO(g)(g, STP)

CO(g) + H2

(g,STP)

HCHO (g) (u,ρ)

2.3

J/m

g~0 J

2.7

J/m

g

CO2(g)+ H2O(g)(STP)


8.8

J/m

g

CO(g) + H2(g) (u,ρ)

4.3

J/m

g

+ 1mg O2

exit293 s

Exit420 s

28

File name

Lifetime of Formaldehyde, τ(T,P)

HCHO + M = H + HCO + M, k=5x1015exp-308kJ/mol/RT cm3/mol-sF. Gernot, D. F. Davidson, R. K. Hanson, Int. J. Chem. Kinet. 36 (2004) 157

1.E-07

1.E-06

1.E-05

1.E-04

1000 3000 5000

Temperature (K)

lifet

ime

(s)


P=1 bar10100

Mechanism:(i) HCHO + M = H + HCO + M

(p) H + HCHO = H2 + HCO(t) H + HCO = H2 + CO(t) H + H + M = H2 + M

(t) HCO + HCO = CO + HCHO

29

File name

Mole Fractions at Equilibrium Formaldehyde expansion from P=22694 bar, T=3732K

[rho=1227 kg/m3,u=1.975 MJ/kg]

Species chamber ε=8 ε=64 species chamber ε=8 ε=64

CO 0.47502 0.48415 0.35692 CH3OH 0.00015 0 0H2 0.39082 0.39891 0.36466 CH3CHO,ethanal 0.00014 0 0H2O 0.06058 0.04282 0.08215 C3H4,allene 0.00013 0 0CH4 0.03818 0.05811 0.05318 C3H6,propylene 0.00013 0 0CO2 0.00856 0.01574 0.05707 CH2 0.00012 0 0C2H2 0.00742 0.00002 0 C2H2,vinylidene 0.00009 0 0CH3 0.00472 0.00001 0 CH2OH 0.00007 0 0H 0.00402 0 0 C3H5,allyl 0.00006 0 0C2H4 0.00267 0.00014 0 C4H2 0.00006 0 0HCO 0.00180 0 0 COOH 0.00005 0 0HCHO 0.00180 0.00003 0 CHCO,ketyl 0.00004 0 0CH2CO 0.00096 0 0 CH3O 0.00003 0 0C3H3,2-pryl 0.00039 0 0 C2H 0.00003 0 0C2H3,vinyl 0.00035 0 0 C3O2 0.00003 0 0OH 0.00032 0 0 C4H6,butadiene 0.00003 0 0C2H6 0.00027 0.00005 0.00001 C2O 0.00002 0 0HCOOH 0.00026 0 0 C2H5OH 0.00001 0 0C3H4 0.00025 0 0 C3H4,cyclo- 0.00001 0 0CH3CO 0.00019 0 0 C3H8 0.00001 0 0C2H5 0.00019 0 0 C4H6,1butyne 0.00001 0 0

C(gr) 0 0 0.08601


30

File name Mole Fractions at EquilibriumFormaldehyde expansion from P=230 bar, T=3433 K,

[rho=12.02 kg/m3,u=1.907MJ/kg]

mole fractions Chambr throat ε=4 e=8 e=16 e=32 e=64CO 0.49263 0.49587 0.49955 0.49553 0.47166 0.43233 0.38881H2 0.47969 0.48865 0.49681 0.4913 0.48006 0.46937 0.46168H 0.02313 0.01223 0.00003 0 0 0 0

H2O 0.00239 0.00173 0.0014 0.00435 0.01321 0.0231 0.03105C2H2,acetylene 0.00105 0.00074 0.00002 0 0 0 0

CH4 0.00032 0.00033 0.00176 0.00435 0.00673 0.00753 0.00728CO2 0.0003 0.00023 0.00041 0.00224 0.01093 0.02605 0.04371CH3 0.00021 0.00012 0 0 0 0 0HCO 0.00014 0.00005 0 0 0 0 0*OH 0.00005 0.00002 0 0 0 0 0CH2 0.00002 0.00001 0 0 0 0 0

HCHO,formaldehy 0.00002 0.00001 0 0 0 0 0C2H 0.00001 0 0 0 0 0 0

C2H2,vinylidene 0.00001 0 0 0 0 0 0C2H4 0.00001 0.00001 0 0 0 0 0C(gr) 0 0 0 0.00223 0.01741 0.04162 0.06748


31

File name

Blowdown from specified initial state (u,ρ) with specified expansion ratio (ε)

1.E-07

1.E-06

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

0 20 40 60 80

COH2CO2H2OHCH4C(gr)

Expansion ratio

Mol

e Fr

actio

nPc=20.2 bar, Tc=3060 K, ρc =1.18 kg/m3


32

File name


22002400260028003000320034003600

0 20 40 60 80expansion ratio

Ve (m

/s)

u(MJ/kg)

3.83.0

ρ(kg/m3)

2.2

1000100101

Mini thruster ε = 8


33

File name


0

500

1000

1500

0 20 40 60 80ε expansion ratio

Ve (p

ress

thru

st) (

m/s

)


34

File name



0.4

0.6

0.8

1.0


α e

xpan

sion

eff

icie

ncy


35

File name


0

1000

2000

3000

4000


Tem

pera

ture

(K)



36

File name


1.E-02

1.E+00

1.E+02

1.E+04


pres

sure

(bar

)Mini thruster ε = 8


37

File name


1.E-03

1.E-01

1.E+01

1.E+03


dens

ity (k

g/m

3)Mini thruster ε = 8


38

File name

Experimental data (I, EL, m) and derived parameters (Cm, Ve, efficiency, EL/m)

Geometry I vs EL slope m vs EL slope Cm Ve Efficiency EL/mmNs/J R2 mg/J R2 Ns/MJ m/s MJ/kg

Mini thruster white 0.444 0.97 0.160 0.99 444 2775 0.616 6.3

Mini thruster black 0.439 0.98 0.156 0.98 439 2814 0.618 6.4

Mini thruster AIR 0.253 0.97 - - 253 - - -

10-cm Model white 0.447 0.85 0.201 0.96 447 2224 0.497 5.0

10-cm Model black 0.453 0.92 0.194 0.93 453 2335 0.529 5.2


39

File name

Conclusions/Work in Progress

• Cm=450 N/MW for Light Craft/Delrin (350 J, 18 µs)• Cm=442 N/MW for Mini Thruster/Delrin (25 J, 18 µs)• 51 % efficiency for EL to jet KE for Light Craft• 62 % efficiency for EL to jet KE for Mini Thruster• Future Experiments

– Vary pulse width, 5 and 30 µs, expansion ratio, ε = 4, 16, …– Increase EL up to ~ 100 J/pulse in mini thruster– Measure time resolved thrust with piezoelectric– Develop chemically enhanced ablative propellants

• Future Calculations with Chemical Equilibrium Applications Code– Factor pressure thrust into analysis– Analyze Chemically Energetic Propellants


40

File name

THE END


41

File name

Φ for Bimodal velocity distribution

Chunks of propellant fheavy mass fraction, vslow velocityHot gases flight mass fraction, vfast velocity

<v>2 = (fheavyvslow + flightvfast)2 <v2> = fheavyvslow2 + flightvfast

2

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0mass fraction of heavy mass

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

= <

v>2 /

<v2 >

r = 1

r = 2

r = 3

r = 4

r = 5r = 6

r = 7r = 8r = 9r = 10

r = 20r = 30

Φ

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0mass fraction of heavy mass

10-3

2344

10-2

2344

10-1

2344

100 r = 1r = 3

r = 4000

r = 20

r = 600

r = high v elocity /low v elocity

Φ = <v>2/<v2> = (fheavy + flightr)2/(fheavy + flightr2) where r = vfast/vslow > 1


42

File name

Divergence Loss

0.92

0.94

0.96

0.98

1

0 5 10 15 20 25 30

half angle α

Rat

io 2

D o

r 3D

to 1

D

NASA 1960

3D: 0.5(1+cos a)

2D: (sin a)/a


α = ½ (divergence angle)

Documents

RECENT LASER PROPULSION RESULTS FROM … · “momentum calorimetry”, in which experiments like those accomplished here may be conducted to obtain reliable heats of formation. The